1. Field of the Invention
The present invention relates to a drilling rig comprising a mast, a drilling drive mounted for displacement thereon, and a drilling element, which can be rotatably driven and moved along the mast by the drilling drive system, the drilling element comprising a continuous screw auger disposed below the drilling drive system and an extension which is connected to the continuous screw auger and which extends upwardly through the drilling drive.
The invention further relates to a drilling method, in which a drilling element is rotatably driven and moved along a mast by means of a drilling drive, the drilling element comprising a continuous screw auger disposed below the drilling drive and an extension which is connected to the continuous screw auger and which extends upwardly through the drilling drive.
2. Description of Related Art Including Information Disclosed Under 37 CFR §§1.97 and 1.98
The use of so-called continuous screw augers for creating bore holes and, in particular, for creating foundation elements has been known for many years. In a continuous screw auger, a drill helix is disposed along the entire length of the drilling bar for the purpose of conveying loosened earth material out of the bore hole toward the surface by means of rotary motion. A continuous screw auger is driven by means of a drilling drive system, by means of which the continuous screw auger is also moved in the boring direction along a usually vertically positioned mast. In this known method, the depth of the bore hole is restricted by the length of the continuous screw auger and the height of the mast.
In order to increase the depth of the bore hole beyond the length of the mast or the length of the continuous screw auger, DE 601 02 255 T2or EP 1 614 853 B1 proposes that an extension bar be disposed at the top of the continuous screw auger, which extension bar extends upwardly through the drilling drive system. The depth of the bore hole can thus be increased by approximately the length of the extension bar.
However, feed helixes cannot be mounted on the extension bar for functional reasons. When sinking a bore hole beyond the length of the continuous screw auger, the earth material excavated can thus no longer be conveyed by the feed helixes up to the surface. This earth material thus accumulates in the bore hole above the continuous screw auger in the region of the extension bar. This can lead to undesirable earth compaction or choking of the bore hole, which makes it difficult to subsequently withdraw the drilling element from the bore hole. Furthermore, the wall of the bore hole can be damaged in this region, which can adversely affect the installation of a foundation element in the bore hole by filling the same with filling material. In order to prevent this, the drilling element must be intermittently removed from the bore hole to remove the earth material. This is time-consuming.